JANESVILLE, Wis. - A carnivorous alien fish known for its voracious appetite and ability to wriggle short distances on land has been found in southern Wisconsin's Rock River.

The discovery of the 2-foot-long giant snakehead by the state Department of Natural Resources marks the first time the species, a native of Asia, has been found in Wisconsin waters, where officials said it may not survive the winter cold.

"This was a real wake-up call," said Mike Staggs, director of fisheries at the DNR.

The giant snakehead can grow to more than three feet in length, and fish managers say that with no natural predator, it could change the local fish population and introduce new diseases.

A year ago, wildlife officials in Maryland killed six adult and more than 1,000 juvenile northern snakehead, a close relative to the giant snakehead, found in a pond.

The DNR found the giant snakehead during a routine fish survey of the Rock River Sept. 4.

The DNR said an employee misidentified the fish as a native bowfin. It was photographed and released before the DNR later concluded it was a snakehead.

Two crews were sent back to the river last Thursday and three more crews went back Tuesday to look for evidence of snakeheads but found none, Staggs said.

Staggs said the results indicate the fish does not appear to be widespread in the river, and the individual snakehead likely was released by a hobbyist after outgrowing an aquarium.

Releasing aquarium fish into the wild in Wisconsin is illegal.

It's unlikely the giant snakehead could survive the cold water of a Wisconsin winter, Staggs said.

flyfisha1

09-25-2003 03:59 PM

Hey Mark,
This hits close to home, since I'm employed by the aquarium industry, and the snakeheads that are being found in US waters are certainly the result of hobbyists ridding themselves of a fish that has grown too large for their current aquarium set up. I was contacted about this issue when it hit the news in Maryland; did a phone interview for the Bassmaster newspaper that's published every couple of weeks.

Snakeheads are a tropcial family, hailing largely from Madagascar. In their home waters, they've ironically been hit pretty hard by the introduction of North American gamefish species such as largemouth bass. Anyone who has kept a snakehead in an aquarium for any length of time will tell you that it's a much more aggressive feeder than any of our native species, and that includes the pike family members, in my opinion. These fish are pike-like in body shape, with a mouth diameter roughly the same as the overall body diameter; they move very quickly in short bursts, having a semi-circular caudal fin shape which is more useful for maneuvering rather than sustained speed. I would think of them as a cross between a largemouth and a pike. These are tropical fish and as such the only way that they'll be able to survive the Winter is to be in an area where heated water enters the system, such as in the outflow of a power plant. Barring that or some similar scenario, those fish are dead as soon as the water temp drops much below 70. The fish grow very rapidly and given the majority of a warm season to exist in a body of water, one fish could do some pretty significant damage to the stock of forage fish and even smaller predatory species, as well as the young of those which grow to larger proportions.

The good news is that fish feed so aggressively and without regard, you could catch one easily with anything that remotely resembles a forage fish. In other words, I wouldn't rank them very high up on the scale of piscine intelligence, so they should be relatively simple to extract from a body of water. Additionally, these guys have the internal morphology of gars and bowfins, so they breathe air and typically hang out at the water's surface, making them easier to spot. Fish for them as you would for pike.

Aquarium hobbyists, I have found, are largely an irresponsible group of people when it comes to providing the proper care and thinking their decisions through regarding fish such as this one that can grow so quickly. Sale of snakeheads in the US should probably be banned, as such.

Dble Haul

09-25-2003 04:03 PM

Thanks for the details. We kicked this around a while ago in another thread (bucket biology rears it's ugly head) about the time they were found in Maryland. From the sounds of their temperature requirements, it seems as if they wouldn't have fared well in Maryland either.

DFix

10-10-2003 11:52 AM

I was about to say something similar to Mark's comment.

Chris - where is it that the water temp dangers info comes from? I'm familiar with those fish from Southeast Asia, but don't remember anything in any news report or anecdotal side story about them being affected by water temp limits.

FrenchCreek

10-10-2003 03:20 PM

Add another question to DFix's psot
Are these critters likely to "adapt" to the colder temps over time?

flyfisha1

10-10-2003 07:14 PM

Hey Guys,
Snakeheads (at least, the species that are kept in captivity by aquarium hobbyists in the US) are tropical fish and have a "comfort zone" of temperature between roughly 70 and 85 degrees; with sustained temperatures below 70 the immune system of the fish begins to fail, making it susceptible to parasite infestations (typically attacking the gills of most fish first, where the most oxygen is present, though in the case of snakeheads, being air-breathers, I can't say whether or not this is the case). The colder the temps and the longer the exposure, the faster the fish dies. It takes many, many generations for a species to be able to adapt to new environmental conditions, as fundamental changes in morphology may be required to cope. That being the case, unless these invading species are able to locate the required water temps throughout the colder months, as well as a source of food, they're extremely unlikely to survive long, particularly now that the cold weather has begun to settle in across the upper states. Addditionally, the fact that the fish must surface to breathe means that any "invaded" bodies of water that freeze completely over are essentially safe, since the fish aren't likely to develop the ability to breathe through gills over the period of a few weeks.
Snakeheads are indigenous to China and Madagascar, as well as other areas throughout Southeast Asia; I'd be worried about the fish if I lived in the southern-most states of the US, but probably no where north of the latitude of Tampa unless the local water has a hot spring or power plant effluent draining in.
Oh, and the reason that there have been few, if any, reports stating that the fish will die in cold weather is that traditionally, it's the procedure of the twits in the news media to blow everything out of proportion before they know all the facts; this is one case where ichthyologists and aquarium hobbyists all over the US were laughing at the supposed "experts" in the fish and wildlife divisions. While I support the claim that these fish can cause significant damage to a fishery by outcompeting native gamefish species for prey (as well as directly eating the gamefish, themselves), I also believe that the fish that have invaded the waters of the Northern US will be dead very shortly.

timwatts

10-10-2003 07:15 PM

Below is some snakehead info from US Fish & Wildlife. It appears that at least one species can live under ice (end of second paragraph). The full document is here. It's a real snoozer. http://policy.fws.gov/library/02fr62193.html

Two larger snakehead species, Channa marulius and C. maruloides, superficially resemble the native bowfin, Amia calva, in that all three are elongated fishes, have long dorsal fins, tubular nostrils, and an ocellus (eyespot) at the base of the upper portion of the caudal fin. The bowfin, however, has its pelvic fins in a more abdominal rather than thoracic or anterior-abdominal position, and the anal fin is not elongated. Moreover, the bowfin does not have a rosette (circular arrangement) of enlarged scales on top of the head.

Species and species complexes of the genus Channa are native from southeastern Iran and eastern Afghanistan eastward through Pakistan, India, southern Nepal, Bangladesh, Myanmar (Burma), Thailand, Laos, Malaysia, Sumatra, Indonesia, and China northward into Siberia. Of the currently recognized 25 species of Channa, 9 species and representatives of 4 species complexes occur in peninsular Malaysia, Sumatra, and/or Indonesia. Of the same 25 species, 16 species and members of 5 species complexes are tropical to subtropical; members of three species complexes are temperate; and one species is temperate to
boreal and can live beneath ice in the northern portion of its range.

The three species of Parachanna are native to Africa and are tropical. Snakeheads are considered as non-ostariophysan primary freshwater fishes (Mirza, 1975, 1995), meaning they have little or no tolerance for seawater. Habitat preferences vary by species or species complex, with a majority occurring in streams and rivers. Others occur in swamps, rice paddies, ponds, and ditches. All can tolerate hypoxic (low oxygen) conditions because they are airbreathers from late juvenile stages. Where known, pH range varies by species with one (Channa
bankanensis) preferring highly acidic (pH 2.8-3.8) waters. At least
three species are tolerant of a wide pH range; C. gachua, C. punctata, and C. striata survived for 72 hours at pH levels ranging from 4.25 to
9.4 (Varma, 1979).

FrenchCreek

10-11-2003 12:21 PM

It great to get valid scienctific reviews about these critters. My contribtion to their eradication will be to send as many "Alberta Clippers" down East this winter as is possible. Humanoids however will need a lot of warm clothes, snow shovels, and such .......

fishboyicu812

10-13-2003 03:46 PM

It seems as if the snakeheads found in Maryland were rather fond of the Old Line State's climate. Or at least comfortable enough to "pump out" a couple of thousand offspring. We have even had a number of pirahana caught in our local waters.(I am not talking about ponds but large brackish rivers.) The neat and or scary part of the story is that in theory they could actually survive our winters due to the availability of warm water discharges in the area.

SDHflyfisher

10-19-2003 08:33 PM

i live within an hours drive of the rock and i am pretty sure if what you guys say about temp that the fish will die off in the winter if not the DNR will do their best i have good confidence in WI DNR

mikez

10-24-2003 03:47 PM

Just to toss in my $00.02.
I also have been employeed in the aquarium idustry at the retail end so I can vouch for the claim that too many in the pet hobbies are irresponsible. The exotic invasives in southern Florida are a case in point. The number of exotic fish, reptiles and birds found in Florida is staggering and growing all the time. I'm refering to reproducing populations, not just your average stray. Many, if not most are released by pet owners. The only reason it is not more widespread in the US is climate.
That mitigating factor becomes moot when temporate species become popular pets. Many states are now passing or trying to pass laws banning specific animals deemed able to reproduce in a temporate climate. Personally, I'm not a big fan of more regulations, but what other option is there? Ironically, many states have F&G regs which prohibit collection of non-game native species thereby preventing concerned hobbiests from keeping only those animals native to their state, regardless of how abundant and secure a given population may be. Kind of a Catch 22.
So what's the answer? Don't know. On one hand, better education of pet hobbiests might prevent some problems. Unfortunately, mis-information or total lack of information is the norm. One need only visit the fish department of any of the supermarket chain type pet stores and ask the teenage clerk a few questions. No help there!
On the other hand, promoting the collecting and culture of secure, abundant native species would at least slow down the importation of exotics. Unfortunately, that is a concept which is generally viewed in a dim light by most state DMR - F&G types. To me, that's the ultimate irony. Think about it - what group of people in the history of this country have been responsible for the introduction of the most exotic species? F&G of course! I defy anyone to find a body of fresh water anywhere in the northeast which does not contain an introduced species! Brown trout, rainbow trout, largemouth bass, bluegill, northern pike etc etc. Our tax dollars and license fees have paid for those exotic introductions and I rarely hear anyone complain!

Oh, and for what it's worth, I've delt with various species of snakehead in the past. One thing is for sure - they are almost industructable! They certainly CAN "breath" air in the traditional fish way, via their gills. The fact that they can also take atmospheric air from the surface means they can live in degraded, oxygen poor, polluted waters which would kill most other fish. Also, I have known them to be kept for years in unheated room temp tanks in New England so a low end temp of 70 F is pretty optimistic. Personally, I'd place it at least 10 degrees lower, if not more.